The present invention relates generally to capturing images of an eye, and more particularly, to a method and apparatus for eye imaging with position registration and constant pupil size.
In the U.S., approximately 17 million people have diabetes; worldwide there are about 170 million. According to a recent estimate, at the current rate of increase, due to genetic makeup and economic growth, it is expected that the worldwide total population of diabetics may reach half a billion by 2008.
An important aspect of the management of diabetes is the constant monitoring of the blood serum glucose level. Current glucose measurement techniques involves pricking the finger with a lancet, and wicking the blood onto an electrochemical test strip that provides the electrical data read by a glucose meter. Many patients attempt to avoid these painful and uncomfortable tests, to the detriment of their health. The problem is especially acute among children.
To address the problem raised by invasive glucose measurement techniques, several non-invasive diagnostic methods have been proposed. One non-invasive diagnostic method for measuring glucose and other analytes of biomedical interest in humans is measuring changes in images of the eyes. This technique is based in part on the fact that some features of the eye have long term stability and that each individual has a unique iris pattern. Also, as the eye is self-cleaning, therefore minimizing contaminants that could interfere with the measurements, it provides an ideal site for diagnostic measurements.
In this method, images of the eye are captured and processed with a complex and sophisticated algorithm to determine a corresponding glucose level in the blood serum. However, in order to make consistent comparisons of the image data, it is necessary to hold constant some of the variables, such as the radiation wavelength and intensity, radiation pulse duration, orientation of the eye, and area coverage of the eye. Although the radiation and other characteristics may be easily reproduced, as they are provided by electronic devices and circuits, it is difficult to manipulate the eye orientation with respect to the measuring instrument, area coverage, and iris area of the eye to achieve consistent results using eye imaging techniques.
Accordingly, there is a need to overcome the issues noted above to achieve imaging of the eye with consistent parameters.